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authorHeiko Carstens <heiko.carstens@de.ibm.com>2013-01-14 19:55:55 +0400
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2013-01-16 18:57:52 +0400
commited4f20943cd4c7b55105c04daedf8d63ab6d499c (patch)
tree3737b2efcd486670eac2cbf5a93bb8fb90964b05 /arch/s390/kvm/interrupt.c
parent7bdc229fad1d42beda70f1966042262470660082 (diff)
downloadlinux-ed4f20943cd4c7b55105c04daedf8d63ab6d499c.tar.xz
s390/time: fix sched_clock() overflow
Converting a 64 Bit TOD format value to nanoseconds means that the value must be divided by 4.096. In order to achieve that we multiply with 125 and divide by 512. When used within sched_clock() this triggers an overflow after appr. 417 days. Resulting in a sched_clock() return value that is much smaller than previously and therefore may cause all sort of weird things in subsystems that rely on a monotonic sched_clock() behaviour. To fix this implement a tod_to_ns() helper function which converts TOD values without overflow and call this function from both places that open coded the conversion: sched_clock() and kvm_s390_handle_wait(). Cc: stable@kernel.org Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kvm/interrupt.c')
-rw-r--r--arch/s390/kvm/interrupt.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index c30615e605ac..82c481ddef76 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -408,7 +408,7 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu)
return 0;
}
- sltime = ((vcpu->arch.sie_block->ckc - now)*125)>>9;
+ sltime = tod_to_ns(vcpu->arch.sie_block->ckc - now);
hrtimer_start(&vcpu->arch.ckc_timer, ktime_set (0, sltime) , HRTIMER_MODE_REL);
VCPU_EVENT(vcpu, 5, "enabled wait via clock comparator: %llx ns", sltime);